REMEMBER Simon Patterson? He was shortlisted for the 1996 Turner Prize for that London Underground poster with all the stations renamed after philosophers, footballers, screen stars and other celebrated figures. It was called The Great Bear. The Tate bought one. The public bought many. People pored over its teasing connections, trying to work out the significance of lines linking Titian to Rupert Murdoch. It became - and arguably remains - the only truly popular hit of Britart. But once you had realised there was no special significance to the system of names on the map, then the joke felt less charming. What might have seemed more sustaining than so many of the one-shot works of that era - the shark, the blood-head, the mutant mannequins - turned out to have very little staying power.

And what about Patterson himself - where should he go from here? It is a question that has dogged most of his contemporaries, artists whose early successes were based on short, sharp, epigrammatic pieces that only needed to be seen once, artists who lived or died by ideas. Some have diversified in medium - Damien Hirst into painting, installation, video, gewgaws; the Chapmans into carving and etching; Marc Quinn into DNA and Carrara marble. Others have continued to come up with new ideas. Mark Wallinger has done both, experimenting in all media as the decades pass and with a high ratio of brilliant coinages and inventions to duds. But Patterson still seems stuck with that map.

The Great Bear is the first work you see in his sizable one-man show at the National Maritime Museum and it is the key, if not the sole source, of everything that follows. Outsize slide rules, for instance, have been inscribed with parallel time lines. Each is a form of lineage - evolutionary, philosophical (Schopenhauer out of Kant and so on), religious (the good old X begat Y of the Bible). And each is more or less dubious. Naturally, you wonder what would happen if you manipulated the rule, and whether these versions of history are somehow related.

That's the tease, at any rate. But you cannot touch the object because it is in a glass case and the puzzle it offers is also out of bounds. Everything remains in deadlock. Systems, classifications and measures are aligned with hearsay, received wisdom and common knowledge, with the implication that the objective and the subjective are equally unreliable.

Four industrial-scale abacuses are named after ships from the ill-fated White Star Line - Olympic, Britannic, Gigantic and Titanic. Each has a different configuration of beads. You could spend time trying to work out what, if anything, these configurations represent - numbers of passengers, voyages, drownings, who knows? But the objects themselves are sullenly resistant, inert.

Patterson has another version of the name game in which he simply prints a name on an unrelated object: Yuri Gagarin, Elizabeth Taylor, written on a blank white canvas. Around the time of the Turner Prize, he said these works were about the predicament of the artist faced with just such a canvas. I hope that's true, because it is a far more poetic image than that of an artist who is just plain stumped.

What's in a name? Yuri Gagarin is emblazoned, again, on a complicated kite made of sailcloth floating among the rafters above the stunning main hall. Is it a drifting memorial, a fragile monument to the great cosmonaut or just a nautical pun? For answers, consult the three fully-rigged sails marooned on the floor elsewhere in the show that bear the names of three writers: Laurence Sterne, Raymond Chandler, Currer Bell. If I tell you that the two major works here are also based on maps - old sailors' charts of unknown waters and star charts of outer space - you will easily match subject to map. One touches upon Jacques Cousteau, the other upon Deep Purple, and both feature bits of biography, misinformation and legend.

There are no pleasingly artful coincidences of data and display, no verbal-visual metaphors, just the crass play upon sailors and stars. Cosmic Wallpaper looks wonderful because it is based on John Cox and Richard Monkhouse's design for a book called Colour Star Atlas, just as The Great Bear relied on Harry Beck's classic Tube map. But Patterson has long since run out of ideas. His early works had a tinge of melancholic wit, a comical mismatch between sublime and banal that could arrange the Apostles in football formation or give the crown of King's Cross to Piero della Francesca. But the later works are dismally nerdish: embarrassing. If you still have The Great Bear in your house, you probably stopped looking at it long ago but at least you have the best of Patterson, the best work he's made in more than a decade.